Sleep disorders are common in pregnancy and disturbances to maternal sleep adversely affect pregnancy outcomes. Maternal sleep comprises, on average, 87 days of a full term pregnancy yet little is known about the role of normal or disordered sleep on the developing fetus. Our objective is to bring measurement of the fetus, using leading edge technologies which include the recent advancement in procuring fetal electrocardiogram (ECG) data in the antepartum, to the field of pregnancy sleep research. We propose that the fetus reacts to the physiological changes that accompany normal and that disordered maternal sleep and chronic sleep disturbances have persistent effects on fetal neuromaturation. To evaluate this premise, we will a) record fetal ECG continuously during nocturnal maternal sleep at 28 weeks gestation while participants are undergoing polysomnography, and b) record fetal neuromaturation indicators during daytime maternal wakefulness at 28 and 36 weeks gestation to evaluate functioning in relation to polysomnography-detected sleep disordered breathing and self-report of habitual sleep characteristics in a sample of 130 obese pregnant women. Fetal neuromaturation measures include fetal heart rate and variation, motor activity, and somatic- cardiac coupling. We focus on obese women because, while sleep disordered breathing has been shown to exert additional independent risk to pregnancy outcomes above that conferred solely by obesity, obesity is the primary risk factor for obstructive sleep apnea and other sleep disturbances in pregnancy. We predict that: 1. obstructive sleep apnea as well as milder forms of sleep disordered breathing will be contemporaneously associated with decelerations in fetal heart rate and reduction in heart rate variability during the night; 2. fetal heart rate and its derivatives will vary by maternal slep stage; 3. sleep disordered breathing will have residual effects on fetal neuromaturation that will be evident in daytime recordings during maternal wakefulness; and 4. maternal perception of sleep quality and disruption will be reflected in alterations to fetal neuromaturation between 28 and 36 weeks gestation. This project will forge an interdisciplinary team of technical and clinical expertise with long-standing independent research programs on both sleep in pregnancy and fetal neurodevelopment. Results will provide new information on the interface between maternal sleep and fetal neurological development and will have implications for clinical management of pregnancy with respect to both sleep disorders and obesity. If successful, we hope these findings will generate a new and productive avenue of inquiry regarding the potential fetal programming effects of disordered maternal sleep as well as essential understanding of the interface between maternal sleep and fetal functioning.